Ch 5. Principles of Inheritance and Variations (Stack 1)

Question 1

Define Genetics

Answer 1

Genetics is the branch of science which deals with the study of inheritance, as well as the variation of characters from parent to offspring.

Question 2

Define inheritance. (K) / Define heredity

Answer 2

Inheritance is the process by which characters are passed on from parent to progeny.

Question 3

Define variation

Answer 3

Variation is the degree by which offspring differ from their parents

Question 4

Define a gene.

Answer 4

Gene is the unit of inheritance which contains the information that is required to express a particular trait in an organism.

Question 5

Define alleles.

Answer 5

Genes which codes for a pair of contrasting traits are known as alleles. they are slightly different fonns of same gene

or

Alternate forms of a gene are called Alleles.

Question 6

What is a dominant allele?

Answer 6

It is one of pair of genes which can express itself whether present in homozygous or heterozygous state.

Question 7

What is a recessive allele?

Answer 7

The allele which is unable to express in the presence of its contrasting factor in a heterozygous condition is called recessive allele.

Question 8

What is genotype?

Answer 8

It is the genetic constitution of an individual with regard to one or more characters irrespective of whether the genes are expressed or not.

Question 9

What is phenotype?

Answer 9

It is the observable or measurable distinctive structural or functional characteristic of an individual with regard to one or more characters.

Question 10

What are homozygous individuals?

Answer 10

Individuals which have the identical alleles of a gene or factors of a character on homologous chromosome

Question 11

What are heterozygous individuals?

Answer 11

Individuals which have the two contrasting factors of a character or two different alleles of a gene on homologous chromosome.

Question 12

What is a true breeding plant?

Answer 12

A true breeding plant is one that, when self-fertilised, only produces offspring with the same trait.

True breeding organisms are genetically identical and have identical alleles for a trait.

Question 13

What is monohybrid cross?

Answer 13

It is a cross between two organisms of a species which is made to study the inheritance of a single pair of alleles or factors of a character.

Question 14

What is Punnette square?

Answer 14

Punnette square is a graphical representation to calculate the probability of all possible genotypes of offspring in a genetic cross.

Question 15

Mention the phenotypic ratio of monohybrid cross.

Answer 15

3:I

Question 16

Mention the genotypic ratio of monohybrid cross

Answer 16

l :2:1

Question 17

What is a test cross?

Answer 17

The crossing of an organism with a homozygous recessive parent in order to determine whether it is homozygous or heterozygous for a particular character is called a test cross.

Question 18

Mention monohybrid test cross ratio

Answer 18

1:1

Question 19

Mention the significance of test cross

Answer 19

The purpose of a test cross is to determine if this individual is homozygous dominant or heterozygous

Question 20

State the law of segregation.

Answer 20

Law of segregation states that “Though the parents contain two alleles during gamete formation, the factors or alleles of a pair segregate from each other such that a gamete receives only one of the two factors”

Question 21

Mention the botanical name of the plant used by Mendel

Answer 21

Pisum sativum

Question 22

How many traits were studied by Mendel

Answer 22

Seven pairs

Question 23

Name the technique used by Mendel to prevent self pollination in pea flowers

Answer 23

Emasculation

Question 24

Differentiate between homozygous and heterozygous conditions.

Answer 24

Homozygous

1. 1. Both the alleles of a character are similar.
2. It produces only one type of gamete.
3. It gives rise to similar homozygous individuals.

Heterozygous

1. It carries dissimilar alleles.
2. It produces two types of gametes.
3. It gives rise to different types of genotypes.

Question 25

Differentiate dominant and recessive alleles

Answer 25

Dominant Alleles

(i) It is able to express itself even in the presence of its recessive allele.
(ii) Its effect can be seen in both heterozygous and homozygous condition

Recessive Alleles

(i) Recessive allele or factor is unable to express its effect in the presence of dominant.
(i) Its effect can be seen only in homozygous condition.

Question 26

Define incomplete dominance

Answer 26

Incomplete dominance is the phenomenon where none of the two alleles of a gene is dominant over each other so that when both of them are present together, a new phenotype is formed which is somewhat intermediate between the independent expression of two alleles.

Question 27

Mention the phenotypic ratio and genotype ratio with respect to incomplete dominance in Snapdragon

Answer 27

1: 2:1

(RR) Red: (Rr) Pink: (rr) White

Question 28

What is incomplete dominance?

Mention an example

Answer 28

Incomplete dominance is the phenomenon where none of the two alleles of a gene is dominant over each other so that when both of them are present together, a new phenotype is formed which is somewhat intermediate between the independent expression of two alleles.

Example: Inheritance of flower colour in Antirrhinum or snapdragon.

Question 29

Define codominance

Answer 29

When two alleles for a trait are equally expressed with neither being recessive or dominant, is called codominance.

Question 30

What are multiple alleles?

Answer 30

When there are more than two, alleles, governing the same character is called multiple alleles .

Question 31

Mention an example for multiple allelism

Answer 31

Inheritance of ABO blood groups system is an example

Question 32

How many genotypes are possible for the four blood groups in ABO blood group system?

Answer 32

Six genotypes are possible

Question 33

A child has blood group ‘O’. If the father has blood group ‘ A’ and mother blood group ·B’, work out the genotypes of the parents and the possible genotypes of the other offspring.

Answer 33

A child with ‘ O’ blood must have the homozygous recessive condition for the character.

Paternal contribution and maternal contribution of a recessive allele each. Hence, the father must have I^Ai and mother must have l^Bi alleles.